Spores are known to form from aerobic Bacilli, anaerobic Clostridia, selected sarcinae and few actinomycetes. Spores resemble certain plant seeds in that they do not carry out any metabolic reactions. In this regard, they are especially suited to withstand severe environmental stress and are known to survive prolonged exposures to heat, drying, radiation and toxic chemicals. These properties make spores especially difficult to kill in environments, like living tissue or objects which come in contact with living tissue, which would be adversely effected by extreme conditions.
Pathogenic spore-forming bacterial like Bacillus anthracis, Clostridium botulinum, C difficile, C. perfringens and C. tetani form spores which survive in harsh environmental conditions for extended periods. The spore nucleoid structure is surrounded by protective layers composed of peptidoglycan and proteins with unusual amino acid contents. This structure provides unique resistance properties acting as a permeability barrier to prevent access to the underlying spore protoplast. Spores are able to survive exposure to chlorinated solvents, detergents, mechanical disruption, extreme temperatures, UV and ionizing radiation. Hence, there is a need to develop a means to prevent the spread of spores once they have contacted a surface.
Most conventional liquid sporicidal agents fall into three broad categories: halide releasing compounds (hypochlorites and idodophores), reactive oxygen releasing agents (peroxides and peracetic acid) or aldehydes (formaline and glutaraldehyde). Activity of all of these agents depends on destruction of fundamental metabolic processes and organic structures making them extremely hazardous to humans. Furthermore, many of these agents rely on the generation of very reactive chemical species, making them inherently unstable. Most commercial sterilants require activation immediately prior to use and loose effectiveness within hours after application. The efficacy of some agents such as hypochlorites is rapidly attenuated by the presence of organic matter. Aldehydes are effective sporicides only at relatively high concentrations (2-10%) as liquids and require high relative humidity for effectiveness as a vapor. Building decontamination has utilized extremely toxic gases such as ethylene oxide, chlorine dioxide and methylene bromide. As with the aldehydes, sporicidal efficacy of these gasses requires high relative humidity and extreme caution must be exercised during use. The ability to determine the successful removal of spores from a surface using one of the aforementioned processes is difficult.
One method for decontaminating biological spore contamination has involved the use of a spore germination composition, over a sufficient time period, to cause germination of the biological spores. With the spores germinated within a contaminated area, select disinfectants show increased effectiveness against the spores. Upon germinating, the spore cortex breaks down, losing heat and chemical resistance, which results in increased susceptibility to being killed by the decontaminant. This method fails to eliminate the problem of successfully removing spores from the surface. Rather, it requires the spores to become part of the surface and to undergo germination prior to removal.
Giletto et al. in U.S. Pat. No. 6,569,353 describe a formulation for decontamination which includes a sorbent material or gel, a peroxide source, a peroxide activator, and a compound containing a mixture of KHSO3, KHSO4, and K2SO4. The formulation is self-decontaminating and once dried can easily be wiped from the surface being decontaminated. This formulation, although useful for an already decontaminated surface, is ineffective as a preventative means for keeping a surface free of contamination.
DiMarzio et al. in U.S. Pat. No. 6,235,351 propose a method for producing a self-decontaminating surface. The method includes exposing a surface to be treated to ultraviolet light and then applying a coating of nanoparticles of a transition metal oxide to the surface. The nanoparticles are heated to 750° C. and sprayed onto the surface to form a nanoparticle coating. The treated surface is exposed to ultraviolet light and water moisture to catalytically form free hydroxyl radicals that thereafter react with contaminants to render them generally harmless. Such a method is cumbersome and not feasible for surfaces that cannot withstand having 750° C. nanoparticles applied thereon.
Buhr et al. in U.S. Patent Application Publication 2005/0191206A1 describe a decontaminating method for biological spore populations which uses the application of an acidic environment to the biological spores with an additional step of moderately heating the biological spores in the acidic environment to decontaminate the spores. As in other methods, this method is only useful for treating surfaces after exposure to biological spores and is not suitable as a preventative measure against spores.
An object of the present invention is to provide a self-decontaminating surface coating or treatment process which, when applied to an article, makes the coated surface of the article hostile towards spores.
Another object of the present invention is to provide a self-decontaminating surface coating or treatment process that facilitates easy removal of spore clusters and elimination of any spore fragments that may penetrate the surface of the coating.
Another object of the present invention is to provide a method for preparing an article that is resistant to spores.